In flat display panels, organic light emitting diode (OLED) display panels have received people's attention widely due to their advantages such as self luminescence, fast response, wide viewing angle, high luminance, fresh colors and being light and thin.
The structure of an OLED usually includes an anode layer, a cathode layer and a luminescent layer disposed between the anode layer and the cathode layer. The luminescence principle of an OLED is as follows. When a voltage is applied between the anode layer and the cathode layer, under the driving of the external voltage, holes injected from the anode layer overcome the interfacial barrier and are transported into the luminescent layer, and electrons injected from the cathode layer overcome the interfacial barrier and are transported into the luminescent layer. Holes and electrons arriving in the luminescent layer recombine to form excitons that experience radiative transitions to bring about luminescence, namely electroluminescence. According to different light emitting surfaces, OLED display panels may be classified into top emitting and bottom emitting types. An OLED display panel includes a pixel array.
In order to increase light transmittance, thin transparent conducting materials are required for the cathode. However, a thin transparent cathode has a high sheet resistance, and a large voltage drop would occur when a current flows through the cathode. Therefore, the farther a pixel is from the power supply point, the smaller cathode voltage it obtains, which leads to a lower display luminance of the pixel than a pixel closer to the power supply point, thereby deteriorating the luminance uniformity of the OLED display device.